Rationalizing the catalytic performance of γ-alumina-supported Co(Ni)–Mo(W) HDS catalysts prepared by urea-matrix combustion synthesis |
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Authors: | Sergio L González-Cortés Serbia M A Rodulfo-Baechler Tiancun Xiao Malcolm L H Green |
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Affiliation: | (1) Laboratorio de Cinética y Catálisis, Departamento de Química, Facultad de Ciencias, Universidad de Los Andes, Mérida, 5101, Venezuela;(2) Wolfson Catalysis Centre, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK |
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Abstract: | A comparative study of the influence of Co (or Ni) promoter loadings and the effect of different sulfurizing agents and sulfurizing
temperatures on the structure, morphology and catalytic performance of Mo- or W-based hydrodesulfurization (HDS) catalysts
was carried out. Catalyst performance using a tubular fixed-bed reactor and the HDS of thiophene as a model reaction was evaluated.
The oxidic and sulfurized states of the HDS catalysts were characterized by laser Raman spectroscopy, thermogravimetric analysis
(TGA), differential scanning calorimetry (DSC) and high resolution transmission electron microscopy (HRTEM). It has been found
that the urea-matrix combustion (UMxC) synthesis is a simple tool for preparing supported catalysts in a short period of thermal
treatment. Several consecutive stages such as urea melting, metal precursor dissolution and chemical reactions take place
before and upon combustion process. The C4H4S/H2-activated Co- (or Ni-) promoted MoS2 (or WS2) catalysts present a strong synergistic effect (SE) when the Co (or Ni)/Mo (or W) molar ratio is near to 0.5, whereas the
C4/C
4
=
molar ratios display a weak antagonistic effect. Alumina-supported Ni–W catalyst showed an optimal SE 2.5 times higher than
those for Co (or Ni)-promoted Mo HDS catalysts. The kinetic parameters for thiophene-HDS reaction were also determined, suggesting
that the C–S bond cleavage reaction for alumina-supported Co(Ni)–Mo HDS catalysts and H2 activation reaction for Ni-promoted WS2catalysts play an important role in the rate-limiting step. |
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Keywords: | HDS catalysts Ni-promoted WS2 catalysts Co(Ni)-promoted MoS2 catalysts urea-matrix combustion synthesis |
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